As this type of invention, there has conventionally been known a heat dissipation device such as the one described in, for example, PTL 1, which has a base part, protruding pieces protruding upward from the right and left ends of the base part, a plurality of fins (3) protruding outward from each of the protruding pieces, and a power transistor (1) mounted on the base part between the right and left protruding pieces, the heat dissipation device being constituted in a substantially U-shape. Note that numbers in the parentheses are reference numerals used in PTL 1.